1. Field of the Invention
The present invention relates generally to a method of forming an integrated circuit, and more specifically to a method of forming an integrated circuit measuring at least a set of alignment marks of each exposure field of a substrate for immediate correction.
2. Description of the Prior Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion. Transferring of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network or adjacent target portions that are successively patterned with a lithographic apparatus, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction.
As the development of miniaturization of integrated circuits progresses, it becomes a critical challenge to forma desired pattern as well as forming it on a specific position by a lithography process. Consequently, modern lithography apparatuses involve extensive measurement prior to the step of actually exposing or otherwise patterning the substrate at a target location. These operations, being time-consuming, limit the throughput of the lithography apparatus, and consequently increase the unit cost of the semiconductor or other products, specifically as pattern features become smaller and overlay performance requirements become ever more demanding. Therefore, an improved measuring method being time-saving, accurate measuring, simulating and correcting of patterns actually printed on a substrate including deformation of patterns printed on the substrate is urged in current industry.